Neutron reflectivity (NR) was used to study the sorption of Eu(III) by graphene oxide (GO) films exposed to ethanol solution of EuCl3. Most of the earlier sorption studies have been performed using GO dispersed in solution. In contrast, layered structure of GO films imposes limitations for penetration of ions between individual sheets. The analysis of NR data recorded before and after sorption under vacuum demonstrates an increase of GO film thickness due to sorption by 35–40%. The characterization of chemical state of Eu(III) sorbed by GO films by X‐ray absorption near‐edge structure (XANES) in high‐energy resolution fluorescence detection (HERFD) method at the Eu L3 edge reveals that it remains the same as in anhydrous EuCl3. Analysis of all collected data including reference experiments with bulk GO samples allows to conclude that EuCl3 penetrates into GO interlayers with ethanol solution and remains trapped in interlayers after evaporation of ethanol. Sorption of EuCl3 results in nearly complete amorphization of film and likely formation of voids, thus making NR models based on specific volume of unit cell not valid for quantitative evaluation of Eu sorption. Limitations of NR method must be taken into account in future studies of sorption by thin films.

中文翻译：

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中子反射率测试氧化石墨烯薄膜对EuCl3在乙醇溶液中的吸附作用

利用中子反射率 (NR) 研究暴露于 EuCl 乙醇溶液中的氧化石墨烯 (GO) 薄膜对 Eu(III) 的吸附3。大多数早期吸附研究都是使用分散在溶液中的 GO 进行的。相比之下，GO 薄膜的层状结构限制了离子在各个片材之间的渗透。对真空吸附前后记录的 NR 数据进行分析表明，由于吸附，GO 膜厚度增加了 35-40%。采用高能分辨率荧光检测 (HERFD) 方法在 Eu L 处通过 X 射线吸收近边结构 (XANES) 表征 GO 膜吸附的 Eu(III) 的化学态3边缘显示它与无水 EuCl 中的情况相同3。对所有收集到的数据（包括使用大量 GO 样品进行参考实验）的分析可以得出这样的结论：EuCl3用乙醇溶液渗透到 GO 夹层中，并在乙醇蒸发后保留在夹层中。 EuCl 的吸附3导致薄膜几乎完全非晶化并可能形成空隙，从而使得基于晶胞比体积的 NR 模型对于 Eu 吸附的定量评估无效。在未来的薄膜吸附研究中必须考虑 NR 方法的局限性。